Cross Polarization Interference Cancellation (XPIC)

Cross Polarization Interference
Cancellation (XPIC)
Topics of Discussion

What is XPIC?

Examples

Design Considerations
General Comments

Some carrier’s transport system designers are
not aware that more than one RF channel may
be assigned to a path

Some also believe that if you do assign a
second channel on a path that another antenna
is required

And most do not know about XPIC and what it
allows a design engineer to accomplish
Disclaimers

This presentation is not a sales pitch for NEC
equipment

According to Dick Laine at Harris Corporation a
similar capability is available for their Megastar
Radio
UPDATE 18 March 2004

Alcatel has XPIC capable equipment. It is
available in the ETSI high capacity radios such
as the 9600 LH and UH, as well as the 9600
USY ("MDR-9000"). Contact your Alcatel
representative for additional information.
Disclaimers

The presenter only has experience with NEC
XPIC equipment

Becky Holland and Bruce Blain of NEC wrote
an article for RadioResourceMagazine
 Information
from that article is presented
with the permission of Bruce Blaine
What is XPIC?

Cross Polarization Interference
Cancellation (XPIC)

How does microwave radio having XPIC
capabilities effectively double the potential
capacity of a microwave path?
What is XPIC?

It allows the assignment of the same frequency
to both the vertical and horizontal polarization
on a path

Where available frequencies are limited then it
is possible to assign the same frequency twice
on the same path using both polarizations
What is XPIC?

Using standard microwave equipment from any
of the major manufacturers, if a full block of
eight frequencies were available for a 6 GHz
lower band path then eight frequencies could
be assigned in each direction on the path, four
per polarization

Using equipment with XPIC capability sixteen
frequencies may be assigned each way on the
same path, eight per polarization
What is XPIC?
Standard Frequency Assignments
XPIC Frequency Assignments

4 Frequencies – Horizontal
8 Frequencies – Horizontal

4 Frequencies – Vertical
8 Frequencies - Vertical
Design Considerations

The use of XPIC requires very high cross
polarization discrimination antennas such as
Andrew HSX-40 dB Cross Polarization
discrimination

XPIC should be considered in the initial system
design – retrofitting the equipment with the
required intra bay cables is not easy after the
equipment is installed, in fact NEC engineers
told me that it cannot be retrofitted in the field
Design Considerations

NEC prefers to have ATPC operational on
paths using XPIC equipment

ATPC must be turned ON for both directions of
a path

Adjacent frequencies on a path should be
receiving at nearly the same level in order for
XPIC equipment to work properly
Design Considerations

For Example, if 13T requires ATPC to clear an
interference case then 12T and 14T are also
required to use ATPC at the same levels

Designers must employ XPIC for the protection
channel and the first operational channel for
the remaining channels 2 through 7 XPIC may
be applied on a per channel basis
Design Considerations

For circulator coupled XPIC equipment an
additional 7.1 dB of loss for the transmitters
and 7.2 dB of loss for the receivers must be
taken into account in the path calculations

XPIC equipment will work with one transmit
antenna and if required a diversity antenna.
The three-antenna configuration required by
some equipment manufacturers because of
intermodulation is not required
Discussion, Questions, Comments